1. Field of the Invention
The present invention relates to cold-curing, solvent-free, duroplastic two- and one-component polyurethane-polyurea compounds (hereinafter abbreviated as PUR/PU), comprising primary and/or secondary di- and/or polyamines, where optionally the primary amino groups can be present in blocked form, e.g., as ketimines, and polyisocyanates, whose free NCO groups are blocked with specific piperidine derivatives, for coatings, sealing and encapsulating compounds.
2. Discussion of the Background
It is known that polyamines react so fast with polyisocyanates that they cannot be processed, when duroplastic PUR/PU compounds are formed. In contrast, diamines can be processed with polyisocyanates into thermoplastic PUR/PU compounds either in solution or in the melt. In the case of the latter PUR/PU systems that can be processed like a thermoplastic, the properties of the PUR/PU elastomers are improved by introducing urea segments.
Thus, it is not possible to prepare cross-linked PUR/PU systems, e.g., by reacting a diamine with a triisocyanate or vice versa by reacting a tri- or higher functional amine with a diisocyanate. In the DE-OS 10 86 372, coating agents or catalyzed lacquers are disclosed. They are prepared at room temperature by reacting a phenol-blocked aromatic diisocyanate and an amide group-containing amine. ##STR1##
A prerequisite for this reaction--reduction of the NCO reactivity with respect to the NH.sub.2 groups by blocking the NCO groups--is that the blocking agent is bonded only so strongly that it can be displaced by the amino group at room temperature, as is the case, of course, for the phenol-blocked aromatic NCO groups. At the 1980 Fatipec Convention (FatipecKonoressbuch II, pp. 293-306), flexible, cross-linked two-component PUR elastomer systems were presented that were prepared according to the same principle - reduction of the NCO reactivity through blocking. These cross-linked 2-component-PUR elastomers are a polymeric network, which is obtained by reacting a nonyl phenol-blocked isocyanate adduct comprising 1 mole of polypropylene ether triol (molecular weight: approximately 3,000) and 3 mole of toluylene-diisocyanate (TDI) with a diamine, e.g., LAROMIN.RTM. C 260 of BASF (3,3'-dimethyl-4,4'-diaminedicyclohexyl-methane) at room temperature in a NCO:NH.sub.2 ratio of 1:1.
Both of the above-described PUR systems cross-linked by a NCO/NH.sub.2 reaction have the drawback that they are not light resistant, since they utilize aromatic polyurethanes, which tend, as is well-known, to discolor during weathering.
It is not possible to eliminate this drawback of the aromatic PUR systems through simple substitution of the aromatic diisocyanate with a (cyclo)aliphatic one (aliphatic polyurethanes exhibit, as is well-known, excellent light resistance and weathering resistance), since phenol-blocked (cyclo)aliphatically bonded NCO groups do not react with amino groups at room temperatures, i.e., the deblocking of these NCO groups by the amino groups does not take place.